Flapping wing is the main dynamical structure of a flapping wing machine. The flapping wing generates lift force and forward propulsion by acting on air. In principle, modern ornithopter imitates the flapping wing of birds and insects. From the perspective of bionics, the flapping wing of current flapping wing machine (ornithopter) is a film fixed on a specific frame. Generally, the structure of the frame imitates the wing structure of the birds and insects. When the flapping wing beats up and down according to the fly-behavior of birds or insects, motive power is generated by the turbulent air around the flapping wing.
Because it is based on the perspective of bionics, the designed flapping wing is composed of a one-piece film, or with a plurality of holes that can reduce the resistance when the flapping wing flaps up, consequently the most area of the flapping wing is covered by a big film. Because of the existence of the big film, the bionic flapping wing is subject to strong resistance when it flaps up and down. When the flapping wing flaps up, it is subject to air resistance which blocks the rising of the aircraft. In order to reduce the air resistance that caused by flapping up of the flapping wing, a special requirement for the frame structure is needed. Such design is complicated. Some designs further require the frame structure can change shape according to the flapping so as to reduce the air resistance when the flapping wing flaps up. Just like that birds can change the wing shape according to the flapping behavior when flapping their wings. From the perspective of bionics, the design of the flapping-wing structure is quite complicated. It is inconvenient to produce and utilize such flapping-wing structure.